Liquid nitrogen transfer system using the leidenfrost principle



D 1970 I D. M. PILLSBURY, JR, ETALYT 3,548,607

LIQL TD NITROGEN TRANSFER SYSTEM USING THE LEIDENFROST PRINCIPLE Original Filed EDQI z ovw INVENTORS M. Pl LLSBURY RU SSELL E HADLEY DONALD United States Patent Office ABSTRACT OF THE DISCLOSURE A transfer system for liquid nitrogen or other liquefied gases working on the Leidenfrost principle which has a smooth but flexible inner tube and a flexible metal outer tube, the latter being impervious to gas and water vapor. The tubing has a special bulkhead connection to the source of liquid nitrogen.

This application is a continuation of Ser. No. 664,539, filed Aug. 30, 1967, now abandoned.

It is an object of the present invention to provide a liquid nitrogen transfer system via the Leidenfrost principle which is flexible yet at the same time prevents the gases and water vapor from penetrating through the inner tubing and freezing therein causing blockage.

Another object of the present invention is to provide a bulkhead connector for the two phase flexible line which does not have to be disconnected from the inside of the cold producing machine.

A further object of the present invention is to return the gaseous nitrogen boil-off from the liquid nitrogen receptacle through the formed space between the outer and inner flexible tubes.

Another object of the present invention is to provide a simplified cryogenic liquid transfer system which is easy to install and operate.

The above and other features, objects and advantages of the present invention will be fully understood from the following description considered in connection with the accompanying illustrative drawings.

FIG. 1 is a cross-section view of the liquid nitrogen transfer system constructed in accordance with the teachings of the present invention.

FIG. 2 is a sectional view of the bulkhead connector for connecting the liquid nitrogen transfer system to the cold producing source.

Referring to FIG. 1 of the drawings the present transfer system utilizing liquid nitrogen and operating on the Leidenfrost principle comprises a flexible conduit referred to generally by the numeral which transfers liquid nitrogen from a liquid nitrogen producing plant 12 to a container, such as a dewar 14. The flexible conduit 10 includes a flexible metal outer tube 16 and a coaxial, smooth vinyl plastic, flexible inner tube 18 lying within the outer tube 16. The space formed between the tubes 16 and 18 respectively bears the reference numeral 20. The liquid nitrogen is transferred in the direction of the arrows through the inner tube 18 from the panel 13 of the refrigerator of plant 12 to the de'war 14. The liquid nitrogen that is boiled off in the inner receptacle of the dewar 14 is conducted through the terminus 22 of the tube 18 into the dewar and is returned back in conduit 23 in the form of N gas to the plant 12 in the direction of the arrows in the space 20.

It should be apparent that if the inner plastic tube 18 was exposed to the atmosphere, gases and water vapor would diffuse through the plastic wall and condense and 3,548,607 Patented Dec. 22, 1970 freeze in the system thereby causing blockage of the conduit and eventual failure of the system. The use of smooth metal lines as an outer tube eliminates the aforesaid problem and prevents the inner tube from being exposed to atmospheric air, however a smooth metal outer tube is rigid and cannot be employed when it is desired to make the transfer system entirely flexible. Therefore, the present metal outer tube 16 is flexible and at the same time is impervious to gases and water. On the other hand, it is required that the inner tube 18 has a smooth surface in order to operate effectively. The returning nitrogen gas located in the space 20 ensures that no gas or water vapor will penetrate the inner tube 18. The fitting referred to generally by the reference numeral 24 has screw connected parts 26 and 28 and the N liquid and the gas lines at this point separate for entry into the dewar 14. The other end of the flexible conduit is provided with a bulkhead connector 30 which is secured to the liquid nitrogen producing plant 12. The bulkhead connector 30 may be disconnected from the bulkhead of the plant 12 without gaining access to the inside of the plant. This is accomplished by inserting the coaxial tube 32 into the bulkhead adapter 34. The tube 32 is held in place by means of helical spring 36 which abuts at one end against the flange 38 of the tube 32. The other end of spring 36 is trapped in cap 40. The latter is screw-connected by coupler 42 to bulkhead adapter 34 that projects out of the liquid nitrogen plant 12. The bulkhead connector 30 is carefully arranged so that the inner tubes 32 and 33 respectively are precisely aligned and there is no gap between the same resulting in failure of the Leidenfrost liquid transfer system. In this regard the tube 32 is spring loaded against tube 33 in the bulkhead adapter 34.

It should be noted that liquid nitrogen droplets flow from the plant 12 to the dewar 14 in the pipe 18 while the nitrogen gas flows in the opposite direction in the space 20.

What is claimed is:

1. In a system operating on the Leidenfrost principle for transferring liquefied gas from a source to a storage receptacle where a quantity of the liquid boils off as gas and is returnable to the source, the improvement in combination therewith of a fluid transfer apparatus, comprismg:

(a) a flexible, plastic inner transfer tube having a smooth first inner passage for liquid,

(b) a flexible, metal outer transfer tube disposed generally coaxially about the inner tube with a first annular space between the tubes for passage of gas, the tubes having first ends connectable to the storage receptacle for communication with the liquid and gas therein, and opposite junction-ends,

(c) coupling means having (i) an external end connected to said junction ends of said inner and outer tubes, and (ii) an internal end releasably connectable to said source, this coupling means having coaxial second inner and annular passages corresponding to and continuous with those of the inner and outer transfer tubes, whereby gas from said receptacle may continuously flow, surround, and insulate the inner tube, and the outer tube prevents water vapor from penetrating the inner tube to the liquefied gas therein.

2. A system as defined in claim 1 wherein said coupling means comprises:

(a) a housing having an internal chamber of first diameter,

(b) a coupling tube having (i) an outside diameter smaller than the housings first diameter, (ii) a first end connectable to said source, and (iii) an opposite junction-end, the tube being disposed in the chamber with its first and junction-ends respectively corresponding to the housings internal and external ends thus defining said second inner and annular passages, the junction-ends of the inner and outer tubes joined to the coupling tube and exterior end of the housing, providing continuous passages (1) through the inner and coupling tubes and (2) through said first and second annular spaces.

3. A system as defined in claim 2 where the source includes first threaded fastening means and wherein said coupling means further comprises:

(a) spring means in said housing urging the coupling tube toward the interior end of the housing, and

(b) a ring-shaped threaded fastener surrounding the housing and connectable to said first fastening means, whereby the coupling tube is then tightly urged against the source.

4. In a system operating on a Leidenfrost principle transferring liquefied gas at cryogenic temperature from a source to a storage receptacle, a fluid transfer apparatus, comprising:

(a) an inner tube formed of plastic flexible at cryogenic temperature, having first and second ends and having an inner passage defined by smooth walls,

(b) a flexible metal housing having first and second ends corresponding to those of the inner tube, and disposed about the inner tube with an annular passage defined therebetween, and

() coupling means (i) at first ends of the tube and housing and (ii) at second ends of the tube and housing for connecting these ends respectively to the source and to the receptacle, whereby liquid is transferrable from the source to the receptacle via the inner passage and gas is ventable from the receptacle to the source via the annular passage, the metal housing providing resistance to penetration of the inner tube and liquefied gas therein by contaminents such as water vapor.

5. A system as defined as claim 4 wherein said housing is an outer tube disposed concentrically about the inner tube.

6. A system as defined in claim 5 wherein said outer tube is a bellows, its walls defining a corrugated edge in longitudinal cross-section.

7. A system as defined in claim 4 wherein said liquefied gas and vapor are nitrogen.

8. A system as defined in claim 1 wherein said liquefied gas and gas are nitrogen.

References Cited UNITED STATES PATENTS 2,838,074 6/1958 Lauck 4 138137X 3,126,711 3/1964 Miller 6252X 3,240,234 3/1966 Bond, Jr. et al 138138X 3,399,691 9/1968 Schoch et al. 6255X 3,418,822 1.2/1968 Massey 6252X 2,722,105 11/1955 Keyes 6255 2,991,633 7/1961 Simon 62514 3,095,711 7/1963 Wurtz, Jr. 62514 3,105,708 10/1963 Esty -154 3,201,947 8/1965 Post, Jr. et. a1 6255 3,302,419 .2/1967 Walter 6255 3,309,884 3/1967 Pauliukonis 6245 3,334,667 8/1967 Hedstrom 6250 3,353,371 11/1967 Hammons et al. 62514 3,364,688 1/1968 Matlow et al. 6245 3,386,256 6/ 1968 Alexander 6255 ALBERT W. DAVIS, JR., Primary Examiner US. Cl. X.R. 

